Method for forming spiral wound synthetic pipes

ABSTRACT

A PIPE IS CONTINUOUSLY FORMED BY SPIRALLY WINDING A BAND ONTO THE CYLINDRICAL PORTION OF A MANDREL AFTER THE BAND EXITS FROM A SYNTHETIC MATERIAL EXTRUDING MACHINE WHILE STILL THERMOELASTIC OR AFTER A PREFORMED BAND IS PASSED THROUGH THE SUITABLE HEATING DEVICE. ONE LONGITUDINAL EDGE OF THE BAND IS PROVIDED WITH A RADIALLY OUTWARDLY WIDENING TONGUE AND THE OTHER LONGITUDINAL EDGE OF THE BAND IS PROVIDED WITH A RADIALLY INWARDLY WIDENING CHANNEL. IN FORMING THE PIPE, THE TONGUE IS COOLED TO BE RIGID AND INSERTED INTO THE THERMOELASTICALLY HEATED CHANNEL OF AN ADJACENT LAP OF THE SPIRALLY WOUND BAND.

Sept 2L 1' M WaENAND ETAL 3,606,670

METHOD FOR FORMING SPIRAL woum) SYNTHETIC PIPES Filed 001:. 2, 1968 3 Sh'eetsSheet 1 FRANZ PRIMESSING FRANZ-WERNER ALFTER BY www- ATTORNEY-5 Sept. 21, 1971 M WIENAND EHAL EfiUfifi? METHOD FOR FORMING SPIRAL WOUND SYNTHETIC PIPES Filed 001:. 2. 1968 s Sheets-Sheet w FIG. 5

' MICHAEL WIENAND KLAUS H3311 HMNZ PHWESSWG FRANZ-WERNER mm W WWfi wlfmw BY Mm ATTORNE Y$ 3 Sheets-Sheet 5 MICHAEL WI KLAUS JENS FRANZ PRIMESSING FRANZ-WERNER ALFTER k m JV V M WIENAND ETAL METHOD FOR FORMING SPIRAL WOUND SYNTHETIC PIPES Filed (M313. 2, 1968 ATTORNEY 5 United States Patent U.S. Cl. 29450 7 Claims ABSTRACT OF THE DISCLOSURE A pipe is continuously formed by spirally winding a band onto the cylindrical portion of a mandrel after the band exits from a synthetic material extruding machine while still thermoelastic or after a preformed band is passed through the suitable heating device. One longitudinal edge of the band is provided with a radially outwardly widening tongue and the other longitudinal edge of the band is provided with a radially inwardly Widening channel. In forming the pipe, the tongue is cooled to be rigid and inserted into the thermoelastically heated channel of an adjacent lap of the spirally wound band.

BACKGROUND OF THE INVENTION It is known to continuously produce pipes by spirally winding bands on a mandrel. For this purpose, bands of a fibrous material saturated with hardenable resins have been employed.

The joining of the individual laps of the wound band with respect to each other is accomplished by havlng the resin cure only during the winding process. A p pe produced in this known manner may consist of several layers of wound or coiled bands.

It is also known to produce pipes by winding polyethylene bands. The edges of the bands are pressed against one another in the thermoplastic range and thus are thereby welded or intimately bonded together to form a pipe. The welding of the longitudinal edges of the band can also be accomplished with the aid of a separate welding wire.

The above-mentioned known processes cannot be employed for all thermoplastic synthetic materials. The quality of the pipes produced is determined by the quality of the welding seam, which seam quality is very different, depending upon the thermoplastic material; for example, the quality of the seam is very poor when polyvinyl chloride is used.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-noted disadvantages. According to the present invention, a profiled band of a thermoplastic has one longitudinal edge provided with a tongue to be interengaged with a channel at its other longitudinal edge, in a dove-tail manner, when the band is spirally wound in a softened condition about a rotating drum serving as a mandrel. The winding is continuous with the channel heated and the tongue cooled so that the thermoelastic channel continuously receives therein the cold tongue of a preceding lap. In this manner, the finished pipe continuously exits from the drum automatically after the seam or joined parts have set, stiffened, hardened, or solidified. The restoring elastic forces of the synthetic channel are utilized for the firm joining of the spirally wound laps.

..It is most. desirable to have the temperature ofthe profiled channel within the upper thermoelastic range during the winding operation, in order to extensively eliminate winding stresses. If the band is conducted to the drum directly from an extruder where it is formed in the thermoplastic range, then an appropriate cooling device must be employed between the extruder and the drum to cool the band to the thermoelastic range. It is also contemplated that the present invention may employ prefabricated bands by heating the channel between the storage roll and the drum in order to bring the channel to the temperature of the upper thermoelastic range.

It is preferable to widen the channel by means of a wedge-shaped tool prior to the profiled band being wound on the drum. By one rotation of the drum thereafter, the band is shifted in the axial direction toward the end of the drum mandrel so that the cold ridge of a preceding wound lap of the band can engage the elastically widened channel of the band that is just being wound upon the drum and still within the thermoelastic range.

After joining, the cooling of the channel assures that the channel will firmly engage the previously cold tongue by shrinkage. If desired, it is further contemplated that the line of separation between the channel and tongue may be further sealed by means of welding after the joining, particularly by blowing welding air against the seam, or gluing, or winding a soft profiled element, for example silicone rubber therewith.

Since shrinkage occurs during the cooling of the pipe, the drum mandrel is conically tapered in the axial direction toward the end from which the finished pipe exits automatically.

Particularly advantageous results are obtained with a rotatable drum acting as the mandrel that has 2. cylindrical portion for holding the two laps in forming the seam and an end conical portion for supporting the thus formed pipe during further cooling. At the entrance end of the cylindrical portion, the drum is provided with a fixed guide plate or wedging tool spirally wound to engage in and spread the channel of the band prior to forming the seam. A plurality of pressure rollers are provided radially opposite from the guide plate at equal spacings along the cylindical portion to press the channel first onto the guide plate and thereafter onto the ridge of the adjacent lap. Also, the drum is. preferably provided with a cooling device for cooling the tongue. The guide plate spirally guides the band onto the drum and widens the channel simultaneously. Also, the guide plate or wedging tool accurately guides the entering channel of the thermoelastic portion of the profile band accurately over the cold tongue of the previously wound portion of the band, that is the adjacent lap.

For the above purpose, the wedging tool is provided with a ridge above the band, which ridge guides the entering profiled band spirally along the drum with a groove guiding the already wound lap of the profiled band having thereon the cold tongue to be joined. The device is further provided with means, associated with the wedging tool, for blowing hot air onto the place Where the tongue and channel of the profiled band are to be joined. Thereby, an intimate, strong, undetachable connection is produced between the tongue and channel.

The axial dimension of the cylindrical portion of the mandrel drum is at least equal to two widths of the synthetic band. The slope of the guide ridge for spirally guiding the band is selected in dependence on the diameter of the drum and the width of the band.

The axial dimension of the conical portion of the drum is to be dimensioned in dependence upon the thermoplastic from which the profiled band is produced, for it is necessary to take into account the differing cooling 3 rates of different materials. The drum mandrel will support the pipe while it is cooled to a self-supporting condition; once the pipe is self-supporting, it may be removed from the drum mandrel. Preferably, a range of 0.2-1.0 times the drum diameter is selected for the conical portion.

Preferably, the pressure rolls are provided with an annular outwardly opening groove corresponding to the exterior configuration of the channel of the profiled band. This has the effect that not only is the surface of the band pressed onto the face of the drum, but also, simultaneously, a sufficient pressure is exerted on the channel for the desired joining with the associated tongue, and the winding process is thus controlled.

It is preferable to mount the pressure rolls so that they may be adjustable with respect to the longitudinal axis of the drum to accommodate different winding angles. This feature assures that the band is pressed flawlessly onto the external surface of the cylindrical portion of the drum.

The cooling device is preferably disposed in the zone of the first two laps of the winding, so that it may cool the continuously effected joint between the tongue and channel on the one hand, and on the other hand cool the tongue of the first lap before it is joined with the associated channel.

BRIEF DESCRIPTION OF THE DRAWING Further objects, features and advantages of the present invention will become more clear from the following detailed description of the drawing, which shows a preferred embodiment of the present invention, wherein:

FIG. 1 is a partial cross sectional view taken spirally along the seam being produced by the apparatus of the present invention somewhat schematically showing the pressure rolls and cooling device;

FIG. 2 is a somewhat schematic perspective view, partially in section, of a portion of the device shown in FIG. 1, with a portion of the pipe having been produced.

FIGS. 3-6 show the profiled band in various stages of the winding process, in section taken through the axis of the mandrel;

FIG. 7 is an external side view of the pipe formed according to the method and apparatus of the present invention',

FIG. 8 is a transverse cross sectional view through a modified band employing the teachings of the present invention and wherein alternately ridges and grooves are formed across the entire width thereof;

FIG. 9 is a transverse cross sectional view through the band of FIG. 8, with the band being thermoelastically deformed, shortly before the cooling process, in a suitable wedging tool, or the like;

FIG. 10 is a transverse cross sectional view through a band that may be employed in combination with the band of FIG. 8; and

FIG. 11 is a transverse cross sectional view through a finished pipe employing interengaging laps that are spirally wound from the bands of FIGS. 8 and 10.

DETAILED DESCRIPTION OF THE DRAWING As shown in FIG. 1, the rotatable drum mandrel 1 cooperates with a plurality of pressure rollers 2 that have relatively fixed axes. A cooling device 3 is disposed adjacent the drum 1 for directing cooling air from suitably apertured pipe manifolds between the rollers 2 and against the profiled band 4 that is spirally wound about the drum '1.

As shown in cross section in FIG. 2, the profiled band 4 is provided with an upstanding tongue 5, a channel 6 and an intermediate web portion. The forwardmost roller 2, as seen in FIG. 2, is provided with a cylindrical portion for engaging the web portion of the band 4 and is provided with an annular grooved portion for engaging the channel 6 of the band 4.

A wedging tool or guide plate 8 spreads apart the channel 6 as the band 4 moves with respect thereto as it is about to be wound on the drum 1, with the leftmost roller 2 as shown in FIG. 1 pressing the band 4 upon the tool 8. Immediately thereafter, the thus widened channel 6 is pressed onto the tongue '5 of a previously wound lap of the band 4 by means of the subsequent rollers 2. A suitable fluid channel is provided as shown in cross section in FIG. 1 through the tool 8 for supplying hot air, solvents, an additional band softer than the material of the band 4, or the like, directly between the interengaging tongue and channel to strike them and enhance the seam. Integrally formed with and depending from the tool 8, there is provided a guide ridge or element 9 for guiding the band 4 on its spiral configuration on the drum 1.

FIG. 3 shows a cross section of the pipe formed with the apparatus and method of FIGS. 1 and 2 taken along the axis of the thus formed pipe, and particularly showing the interengaging channels and tongues of adjacent laps of the spirally wound band.

FIG. 4 is an axial partial cross sectional view through the band and showing the tongue 5 being elastically deformed after leaving the extruding nozzle or plasticizing device in the thermoelastic range. As shown in the right hand portion of FIG. 5, the channel 6 is elastically widened by means of the wedging tool 8 within the thermoelastic region, which wedging tool 8 is integral with the guide element 9.

FIG. 6 shows the interengagement of the band laps of the finished pipe, which view would be an axial cross sectional view of the finished pipe as shown in FIG. 7. The engaging surfaces of the channel 6 and tongue 5 may be bonded, in addition to the bonding occurring by pressure and heat, by adhesives or solvents introduced during the joining.

In the modification of FIGS. 8-11, the same principles as employed above are used to form a finished pipe having plural overlapping layers, which finished pipe is shown in axial cross section in FIG. 11. It is seen that pipes having different thicknesses may be constructed with the bands shown in FIGS. 8 and 10 with the apparatus of FIGS. 1 and 2 employing the wedging tool as shown in FIG. 9. Thus, the tongues I10, and by necessity the channels 11 formed therebetween, of the band according to FIG. 8 are elastically deformed in the wedging tool 12 of FIG. 9 shortly before the winding process where they are interengaged with the similarly formed tongues 10 and channels 11 of the band according to FIG. 10, in the production of the pipe shown in FIG. 11.

Accordingly, by providing several layers of the windings, with the use of the profiled bands as shown in FIGS. 8 and 10, pipes having different wall thicknesses may be produced, as shown in FIG. 11. The operation performed with respect to FIGS. 1-7 is substantially the same as the operation to be performed with FIGS. 8-11, except for the necessary changes mentioned above relating to the different configuration of the bands and the resulting pipe to be formed thereby. Thus, reference will be made to FIGS. 1 and 2 for the operation.

After exiting from the extruder forming the band, or after exiting from the heating device perheating the preformed stored band, the preferably dovetailed groove 6 is elastically widened. As the band 4 is placed on the rotating drum 1, it is pressed by the pressure rollers 2 against the surface of the cylindrical portion of the drum and compressed by cooling air from the manifold of the cooling device 3. In this manner, the tongue 5 is cooled, preferably cooled to room temperature; the channel 6, however, remains so warm that it is still thermoelastically deformable. After one rotation of the drum 1, the band 4 has been axially shifted, with respect to the longitudinal axis of the drum, by one hand breadth, for example, in the direction towards the conical portion of the drum 1.

The cold ridge of the portion of the band 4 already wound upon the drum 1 and the elastically widened channel 6 of the portion of the band entering the drum, which latter portion is in the elastic range substantially Warmer than the previously wound portion, are exactly radially superimposed under the guiding influence of the tool 8 and guide ridge 9 cooperating with the leftmost roller 2 and subsequently continuously joined by means of the following rollers 2. The tongue 5 and channel 6 are firmly pressed into each other by the pressure exerted by the annular groove in each of the rollers -2, which grooves are formed at the ends of the pressure rollers 2. Accelerated by the compressed cooling air from the cooling device 3, the bead provided With the channel 6 cools ofl? and firmly engages, by shrinkage, the cold tongue 5, due to the restoring force present inherently within the material of the band 4, with the cooling being to below 60 C. on the basis of the coefficient of expansion.

The present invention has been disclosed with respect to a preferred apparatus for carrying out the preferred method to produce two embodiments of the pipe. These specific examples have been described in detail rfor purposes of illustration and variations are contemplated within the broader aspects of the invention.

It is claimed:

1. A process for the production of spirally wound pipes from band material joined by means of at least one tongue and groove seam, comprising the steps of feeding indefinite length synthetic band materials having a longitudinal channel and a correspondingly shaped longitudinal tongue;

spirally winding the band on a mandrel in a plurality of adjacent laps;

forcing the tongue of one lap into the channel of the adjacent lap in a continuous manner; and

softening the synthetic material at least in the region of said channel and cooling the tongue prior to the step of forcing the tongue into the channel.

2. The process according to claim 1, wherein a plurality of separate bands are spirally wound on the mandrel simultaneously in overlying relationship.

3. The process according to claim 2, including the step of continuously providing a separate smaller band of material only between said tongue and groove prior to and during the step of forcing said tongue into said groove.

4. The process of claim 1, wherein the step of winding includes winding a first band of material in a single cylindrical path and winding a second band of material on said first band of material in a second cylindrical path concentric with said first cylindrical path in one half lap overlapping relationship with respect to the axial direction of the pipe.

5. The process of claim 7, including the step of continuously interengaging a plurality of radial channel portions and a plurality of tongue portions respectively on each of said first and second bands.

6. The process of claim 1, wherein a plurality of separate bands are spirally wound on the mandrel simultaneously in overlying relationship.

7. The process of claim 1, including the step of continuously providing a separate smaller band of material only between said tongue and groove prior to and during the step of forcing said tongue into said groove.

References Cited UNITED STATES PATENTS 1,688,762 10/1928 Steenstrnp 138-140 2,253,093 8/1941 Raichle et a1. 138l50 2,713,381 7/1955 Scck 2 9453 2,739,089 3/1956 Hageltern 29-453UX 3,199,541 8/1965 Richitelli 138-154X FOREIGN PATENTS 9,498 12/1909 Great Britain 138-147 CHARLIE T. MOON, Primary Examiner US. Cl. X.R. 

